a. Field of the Invention
The invention relates generally to printing and copying systems and in particular to non-impact electronic printing and copying.
b. Prior Art
Previously, most non-impact printers and copiers have relied upon the formation of an electrostatic latent image to which a toner is subsequently applied for forming visible image on paper. In the prior art, others have realized the advantage of omitting the step which consists of forming an electrostatic latent image. In some instances, this has been accomplished by printing directly on paper, by accelerating charged particles and fusing them to paper. For example, in U.S. Pat. No. 3,751,159 Fisher teaches use of a copying system using a wire matrix to accelerate ionized toner particles from a cylindrical bar of compressed toner particles held together by a binder. The bar is spaced from the wire matrix so that a paper web can pass therebetween. The ionized toner particles travel toward the wire matrix when energized until stopped by the paper, thereby leaving a visible image.
In U.S. Pat. No. 3,427,633 Waterman teaches the use of conductive toner particles on and in a web next to scanning electrodes which cause localized heating so that the toner particles are transferred to paper beneath the web by minute explosive action.
In U.S. Pat. No. 3,355,743 Capps teaches that a belt or web can carry toner particles between two electrodes. Sheet material, such as paper also passes between the electrodes. The electrostatic field between the electrodes causes previously charged dielectric toner particles to be accelerated and adhere to the paper.
Previously, electronic dot matrix line printers have relied upon a high voltage discharge between an array of fine wires and a backing electrode, or metallized paper for marking the paper. In some instances, holes were burned in the paper opposite the wires which were energized. In other instances, the paper was responsive to thermal energy generated by the electrode so that a dot was produced in areas of intense localized heating. In still other instances, such as the Fisher Patent, toner particles were caused to become accelerated from the backing electrode and fused to the paper. The dot matrix approach to line printing is extremely useful in digital electronics, especially in computer applications where large amounts of output data exist.
An object of the invention was to devise a non-impact, all electronic printing system which prints at least as well as prior art mechanical printing press systems by relying on dynamic current flow through the recording medium from an eroding electrode of writing material to create an immediate image, rather than from the formation of an electrostatic image requiring further processing and developing.
Another object was to devise a printing system which could be adapted to high speed line printing.
Another object was to devise a standardized miniature printing module which could be used in many kinds of printing instrument such as typewriters and photocopiers.